As your resident telecommunications tech I can tell you with 99.997% certainty what you are looking at: It's a fibre optic line. There's actually 2 of them at your pin-drop.
Several things stand out for me. Mainly that there is a lack of insulators which tell me no power flows along it. I also followed the line south from your pin and on the next high voltage transmission tower (here in western Canada, BC Hydro and TransAlta Utilities call them "structures") I see a fibre loop strapped to the pole. It looks identical to the one suspended over the tracks which also use the same support hardware.
So keeping that in mind I continued south following the uninsulated line supported over the tracks. Eventually it stops and transfers back to a high-voltage structure near Blanco Dr and Witt Rd just north of a substation. It actually pairs back up with the other FO line seen at your pin-drop.
Now, if you are wondering why it would branch off for a ways before rejoining, it's quite possible that it's done as an economic measure. Telecom companies will often lease a spot on a Utility structure (or competitors pole) for a set rate usually by the km or mile. Sometimes it's cheaper to put up your own. I've seen a dozen examples of this in my city.
Hard to tell in the Streetview images but that appears to be a decent sized FO line.